This paper evaluates the possibleconsequences of decreasing in the amount of waterprovided by the irrigation board to the farms, andincreasing in the unitary water charges that theirrigation board applies to the farms. The study hasbeen conducted in a Mediterranean region of southernItaly where farmers can use water delivered by anirrigation board and by privately owned wells. Theresults of the analysis, performed by means of amathematical programming model, show that in bothcases farmers substitute the water supplied by theirrigation board with that extracted from farm wells.This generates an over-extraction of resources from theaquifer leading to likely negative environmentalconsequences. This also endangers the economicsustainability of the irrigation boards, which areinstitutions whose activity can be monitored andinfluenced by public administration bodies.